基于超Nyquist在光通信系统中传输方案的分析

基于FTN(超Nyquist)方案是一种高频谱效率传输方案。文章总结了目前国际上最新的基于FTN传输方案:级联多模盲均衡FTN、数字FTN和SOFTN(软输出FTN)。其中,级联多模盲均衡FTN方案能有效地抑制噪声和信道间串扰,数字FTN方案能有效地简化系统结构,而SOFTN方案的频谱效率最高。对这三种方案的性能和原理进行了详细分析和比较,以期作为未来长距离、大容量光纤通信系统设计的依据。     

Satellite systems for personal communication networks

The paper addresses some issues related to Satellite Personal Communication Networks (S‐PCNs). The role of satellite communications in that scenario is discussed, and some characteristics of S‐PCNs are identified. In addition, the problem of the integration of S‐PCNs with the Universal Mobile Telecommunication System (UMTS) is considered. In this respect an original methodology for accomplishing such integration is proposed; such methodology aims at avoiding complex protocol conversions at the interfaces between the terrestrial and the satellite segment. The paper is partly based upon the work performed by the authors in the framework of the European Community INSURED Project “INtegrated Satellite UMTS Real Environment Demonstrator”. This revised version was published online in June 2006 with corrections to the Cover Date.     

流星突发通信中的增量冗余传输方案

在流星突发通信中,混合ARQ技术能有效保障数据传输的有效性和可靠性。文中通过对传统的增量冗余传输方案进行分析,提出了一种改进的短码字重传冗余HARQ方案,并对单条余迹下两个站点间的数据通信进行了仿真。理论分析和仿真结果表明,改进后的方案能有效抑制噪声干扰,增加吞吐量。     

Handover scheme for mobile cellular communication systems

A new scheme for minimising handover failure probability in mobile cellular communication systems, by exchanging channels between two mobiles moving in opposite directions across the endeavour area of adjacent cells is presented. The performance evaluation of the new scheme is carried out by computer simulation of a two cell model     

Efficient location area planning for personal communication systems

A central problem in personal communication systems is to optimize bandwidth usage, while providing Quality of Service (QoS) guarantees to mobile users. Network mobility management, and in particular, location management, consumes a significant portion of bandwidth, which is a necessary overhead for supporting mobile users. We focus our efforts on minimizing this overhead. Unlike previous works, we concentrate on optimizing existing schemes, and so the algorithms we present are easily incorporated into current networks. We present the first polynomial time approximation algorithms for minimum bandwidth location management. In planar graphs, our algorithm provably generates a solution that uses no more than a constant factor more bandwidth than the optimal solution. In general graphs, our algorithm provably generates a solution that uses just a factor O (log n) more bandwidth than optimal where n is the number of base stations in the network. We show that, in practice, our algorithm produces near-optimal results and outperforms other schemes that are described in the literature. For the important case of the line graph, we present a polynomial-time optimal algorithm. Finally, we illustrate that our algorithm can also be used for optimizing the handoff mechanism.     

一种新型的数字图像/话音传输系统的实现方案

提出了一种采集与传输数字图像／话音的方法，介绍了其总体方案以及设计重点，包括乒乓存储结构的改进、数据复接和控制逻辑的实现等。     

利用WDM和OADM实现铁路各站光接入

文章提出了一种基于密集波分复用器(DWDM)和光分插复用器(OADM)、以物理拓扑为总线型、逻辑拓扑为星形的适合于铁路通信各站光接入的光传输网方案,描述了光节点结构及这种网络的波长重复利用和自愈保护功能,实验测试了逻辑单星形光网络的传输特性,分析了网络规模的限制因素.     

Issues in satellite personal communication systems

In the paper various issues in personal satellite communications are addressed. Basic geostationary and non‐geostationary satellite constellations are considered. The narrowband and wideband characterization of the mobile satellite channel and related system implications are discussed. Satellite diversity is presented as a measure to overcome signal shadowing. The capacity of TDMA and CDMA multiple access is estimated, taking into account co‐channel interference. Various network issues, such as mobility management, radio resource management, call control, routing, and network integration are addressed. Finally, some regulatory and political issues are mentioned which may be most relevant for market development and financial success of satellite personal communication systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

Emerging mobile and personal communication systems

The market demand for wireless communications has been demonstrated by the rapid growth of different second-generation wireless technologies that are optimized for particular applications and environments. Obvious examples include: digital cellular systems like GSM, ADC, PDC,and DCS1800 for widespread vehicular and pedestrian services, and cordless telecommunication systems based on CT2, DECT, and PHS standards for residential, business, and public cordless access applications. Efforts are also underway to consolidate the various radio environments and applications under a single standard for third generation wireless, i.e., FPLMTS. In the area of personal mobility, with the recent availability of “personal” numbers in various countries (e.g., 500 numbers in the United States), many fixed network operators are starting to offer such personal mobility services as “personal number service” and “number portability”. These services represent initial stages of full personal mobility that will be provided by UPT in both wireline as well as wireless environments. The expected heavy demand for PCS in the United States and the underlying market/regulatory forces are driving the standardization and business activity. A number of air interface standards for the 1900 MHZ PCS band are being considered, which are based on TDMA, CDMA, and FDMA technologies singly or in combination. Many are variations of existing digital cellular and cordless telecommunications technologies. PCS networking standards are also being developed; both for standalone systems and for systems that will utilize public switched network capabilities     

An equicorrelation-based multiuser communication scheme for DS-CDMA systems

An equicorrelation-based multiuser communication (ECBMC) scheme for direct-sequence code-division multiple-access (DS-CDMA) systems is presented. The ECBMC receiver has low computational complexity that is comparable to that of the conventional detector. By using the equality of cross correlations, the ECBMC scheme can completely eliminate multiple-access interference (MAI) in a synchronous single-path DS-CDMA network. The system performance is independent of the number of active users. The scheme is extended to include the effects of multipath fading. It is able to suppress a major portion of the MAI. This proposed ECBMC scheme is quite attractive for an MAI-dominant environment.     

A new modulation scheme for IR-UWB communication systems

Since the poor performance of orthogonal binary Pulse Position Modulation (PPM) compared with binary Pulse Amplitude Modulation (PAM), this paper presents a new modulation scheme named Pulse Width Modulation (PWM) for Impulse Radio Ultra-WideBand (IR-UWB) communication systems. This modulation scheme uses pulses with equal amplitude and different widths to carry different information. The receiver employs differences between similarity coefficients among these pulses to distinguish different information. Bo...     

Spectrally efficient MSK scheme for SCPC communication systems

A spectrally efficient scheme is described, for SCPC (single channel per carrier) communication systems, in which slightly modified MSK (minimum shift keyed) channels can be allowed to overlap spectrally, with a channel spacing equal to half the individual channel bit rate, without causing any crosschannel interference     

Generalized correlation-delay-shift-keying scheme for noncoherent chaos-based communication systems

In this paper, we propose a generalized correlation-delay-shift-keying (GCDSK) scheme for noncoherent chaos-based communications. In the proposed scheme, several delayed versions of a chaotic signal are first produced. Some of them will be modulated by the binary data to be transmitted. The delayed signals will then be added to the original chaotic signal and transmitted. At the receiver, a simple correlator-type detector is employed to decode the binary symbols. The approximate bit error rate (BER) of the GCDSK scheme is derived analytically based on Gaussian approximation. Simulations are performed and compared with the noncoherent correlation-delay-shift-keying (CDSK) and differential chaos-shift-keying (DCSK) modulation schemes. The effects of the spreading factor, length of delay, and the number of delay units on the BER are fully studied. It is found that GCDSK can achieve better BER performance than DCSK under reasonable bit-energy-to-noise-power-spectral-density ratios.     

Wideband rectangular slot antenna for personal wireless communication systems

Antenna designs are achieved for wideband operation by the use of a coplanar patch-slot antenna, fed by a coplanar waveguide. This design is easily tuned to operate at 2.45 and 5.75 GHz, with wide bandwidth for wireless systems. The operating frequency is controlled by modifying the patch dimensions. The return loss, input impedance, radiation pattern, directivity, gain, and efficiency of the proposed designs are computed and presented. A parametric study of the antenna is also introduced.     

Three-dimensional cellular systems for air/ground personal communication

A new three-dimensional (3-D) cellular system is proposed for air/ground (A/G) personal communications. The proposed system extends the Global System for Mobile Communication (GSM) to enable its subscribers to send and receive calls while traveling in the air using the same subscriber identity module (SIM)-the same mobile number-that is used for the ground network. Modifications to the GSM system architecture to develop the A/G system architecture are outlined. A multilayer service volume is proposed in which the coverage volume is divided into three coaxial cylindrical layers (cells) with each layer serving a limited part of the airspace. Capacity of the new proposed system based on the standard GSM concept is analyzed and compared to other alternative systems: Code Division Multiple Access (CDMA) and Frequency Division Multiple Access (FDMA).     

Location update optimization in personal communication systems

Mobility tracking is concerned with finding a mobile subscriber (MS) within the area serviced by the wireless network. The two basic operations for tracking an MS, location updating and paging, constitute additional load on the wireless network. The total cost of updating and paging can be minimized by optimally dividing the service area into location registration (LR) areas. There are various factors affecting this cost, including the mobility and call patterns of the individual MS, the shape, size and orientation of the LR area, and the method of searching for the MS within the LR area. Based on various mobility patterns of users and network architecture, the design of the LR area is formulated as a combinatorial optimization problem. The objective is to minimize the location update cost subject to a constraint on the size of the LR area. This revised version was published online in July 2006 with corrections to the Cover Date.